Stimuli and Responses- Control of Heart Rate Flashcards
Where does the process of controlling heart rate start?
In the sinoatrial node in the wall of the right atrium
How is the SAN a pacemaker?
It sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls
What is caused by the SAN acting as a pacemaker?
The right and left atria to contract at the same time
What does a band of non-conducting collagen tissue do?
Prevents the waves of electrical activity from being passed directly from the atria to the ventricles
Where are the waves of electrical activity transferred to from the SAN?
To the atrioventricular node
What is the AVN responsible for?
For passing the waves of electrical activity onto the bundle of His
Why is there a slight delay before the AVN reacts?
To make sure the atria have emptied before the ventricles contract
What is the bundle of His?
A group of muscle fibres responsible for conducting the waves of electrical activity between the ventricles to the apex of the heart
What is the Purkyne tissue?
Finer muscle fibres in the right and left ventricle walls that the bundle of His splits into
What is the role of the Purkyne tissue?
Carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously from the bottom up
What does the sinoatrial node (SAN) do?
Generates electrical impulses that cause the cardiac muscles to contract
How is the rate at which the SAN fires unconsciously controlled?
By a part of the brain called the medulla oblongata
Why do animals need to alter their heart rate?
To respond to internal stimuli
How are stimuli detected?
By pressure receptors and chemical receptors
Where are baroreceptors (pressure receptors) found?
In the aorta and carotid arteries
How are baroreceptors stimulated?
By high and low blood pressure
Where are chemoreceptors (chemical receptors) found?
In the aorta, the carotid arteries and in the medulla
What is the role of chemoreceptors?
Monitor the oxygen level in the blood and also carbon dioxide and pH
How are electrical impulses from receptors sent to the medulla?
Along sensory neurones
What is the role of the medulla?
Processes the information and sends impulses to the SAN along sympathetic or parasympathetic neurones
What is the receptor when there is high blood pressure as the stimulus?
Baroreceptors detect high blood pressure
What is the neurone and transmitter involved when there is high blood pressure/high blood O2/high CO2/low pH?
Impulses sent to the medulla which sends impulses along parasympathetic neurones and these secrete acetylcholine which bind to receptors on SAN
What is the response when there is high blood pressure/high blood O2/high CO2/low pH and acetylcholine is secreted?
Heart rate slows down to reduce blood pressure back to normal
What is the receptor when there is low blood pressure as the stimulus?
Baroreceptors detect low blood pressure
What is the neurone and transmitter involved when there is low blood pressure/low blood O2/high CO2/low pH?
Impulses sent to medulla which send impulses along sympathetic neurones and these secrete noradrenaline which binds to receptors on SAN
What is the response when there is low blood pressure/low blood O2/high CO2/low pH and noradrenaline is secreted?
Heart rate speeds up to increase blood pressure back to normal/to return O2, CO2 and pH levels back to normal
What is the receptor when there is high blood O2/low CO2/high pH or low blood O2/high CO2/low pH as the stimulus?
Chemoreceptors detect chemical changes in the blood
